In related art, there is a known technique of transferring an outgoing call from a base station that received the outgoing call generated at a mobile telephone to another base station that can be connected to a base station control device (for example, refer to Japanese Laid-open Patent Publication No. 2000-50359, the entire contents of which are incorporated by reference herein). There is also a known technique that one base station can reestablish communication through a second base station via a relay station connected to the second base station when the first base station is disconnected from the network (for example, refer to Japanese National Publication of International Patent Application No. 2011-519530, the entire contents of which are incorporated by reference herein). There is also a known technique of radiating radio waves further than a normal radio wave radiation range by changing the tilt angle of an antenna of a base station (for example, refer to Japanese Laid open Patent Publication No. 2011-101328, the entire contents of which are incorporated by reference herein).
There is also a known technique of regulating a coverage of an antenna by adjusting a tilt angle of the antenna of a base station of a handover source (for example, refer to Japanese Laid-open Patent Publication No. 2011-250216, the entire contents of which are incorporated by reference herein). There is also a known technique of transmitting data from one radio terminal to another radio terminal by conducting communication between base stations (for example, refer to Japanese Laid-open Patent Publication No. 2010-114904, the entire contents of which are incorporated by reference herein). There is also a known technique of adjusting the tilt angle of an antenna of a base station when a state in a service area changes due to installation or removal of another base station (for example, refer to Japanese Laid-open Patent Publication No. 2007-36487).